ILOG CPLEX 11.0 User's Manual

The amount of preparation in the first phase and the intensity of exploration in the secondphase are controlled by the pool intensity parameter:●●SolnPoolIntensity in Concert Technology;CPX_PARAM_SOLNPOOLINTENSITY in the Callable Library;● mip pool intensity in the Interactive Optimizer.After a model has been read (or created), the first call to populate will carry out both the firstand second phase. In the general case, subsequent calls to populate will re-use storedinformation and proceed with the continuation of the second phase. The first phase will bere-computed if:◆the value of the pool intensity parameter has increased between successive calls ofpopulate;◆ any filters have been deleted.The details of the algorithm that populates the solution pool are published in the paper titled"Generating Multiple Solutions for Mixed Integer Programming Problems," by EmilieDanna, Mary Fenelon, Zhonghao Gu, and Roland Wunderling, in the Proceedings of theTwelfth Conference on Integer Programming and Combinatorial Optimization IPCO 2007,pages 280 - 294.Example: Calling PopulateYou can generate multiple solutions with populate. To see this effect in the InteractiveOptimizer, first read the example cited in Example: Simple Facility Location Problem onpage 302, like this:read location.lppopulateAt default settings in the Interactive Optimizer, you will see results such as these:Populate: phase ITried aggregator 1 time.MIP Presolve eliminated 3 rows and 3 columns.MIP Presolve modified 47 coefficients.Reduced MIP has 49 rows, 40 columns, and 148 nonzeros.Presolve time = 0.01 sec.Clique table members: 45.MIP emphasis: balance optimality and feasibility.Root relaxation solution time = 0.04 sec.ILOG CPLEX 11.0 — USER’ S MANUAL 307